1. Field of the Invention
The present invention relates to cryotherapy devices and more particularly to an expandable multi-tubular cryoprobe for freezing and destroying biological tissues.
2. Description of the Related Art
Cryosurgical therapy involves the application of extremely low temperature and complex systems designed to suitably freeze the target biological tissue to be treated. Many of these systems use cryoprobes with particular shapes and sizes that are designed to contact a selected portion of the tissue without undesirably effecting adjacent healthy tissues or organs. Extreme freezing is produced with refrigerants that are introduced through a flexible or rigid probe. The freezing is then applied to the target tissue through a heat transfer element formed as a part of the probe and limited to applying the freezing to a relatively small location.
Typically the heat transfer element is positioned at a distal end of the probe. It must be small enough to permit its easy introduction into the treatment area, but, must also provide a tight thermal contact with target tissue, i.e., it must be large enough to contact all the target tissue directly thereby allowing the freezing of all the target tissue in one step.
To realize tight thermal contact between the heat transfer element and the target tissue the distal end of the cryoprobe is conventionally designed with a small balloon that is positioned in the selected location and is then inflated to contact the target tissue, such as the wall of a blood vessel. This inflation may be achieved by expanding a compressed refrigerant into the balloon. Alternatively, it may be achieved by introducing a separate pressurized fluid through the probe into the balloon.
Known cryosurgical devices using inflated balloons are described in U.S. Pat. No. 6,355,029, issued to Joye, et al, entitled, “Apparatus and Method for Cryogenic Inhibition of Hyperplasia”; U.S. Pat. No. 6,537,271, issued to Murray, et al, entitled, “Balloon Cryogenic Catheter”; U.S. Pat. No. 6,685,720, issued to Wu, et al, entitled “Catheter Having Improved Shaped Retention”; U.S. Pat. No. 6,893,433, issued to Lentz, entitled “System and Method for Performing a Single Step Cryoablation”; U.S. Pat. No. 7,022,120, issued to LaFontaine, entitled “Cryoplasty Device and Method”; U.S. Pat. No. 7,220,252, issued to Shah, entitled “Inflatable Dual Balloon Catheter”; WIPO Pub. No. 2005/063136 A2, to Vancelette, et al, entitled “Cryosurgical Devices and Methods for Endometrial Ablation”; U.S. Pub. No. 2004/0148004, to Wallsten, entitled, “Balloon Catheter and Method for Treatment of a Mammalian Duct or Cavity by Pressure or Heat”; U.S. Pub. No. 2006/0212028, issued to Joye, et al, entitled, “Cryosurgical Fluid Supply”; U.S. Pub. No. 2006/0247611, issued to Abboud, et al, entitled “Wide Area Ablation of Myocardial Tissue’; and U.S. Pub. No. 2006/0253114, issued to Saadat, entitled “Methods and Apparatus for Cryo-Therapy”.
U.S. Pub. No. 2006/0247611, issued to Abboud, et al, entitled “Wide Area Ablation Of Myocardial Tissue”, discloses a distal end of the cryoprobe which is axially movable by means of a pull wire that simultaneously deforms a flexible element connected to an inflatable balloon that can expand radially from an initial diameter to a final diameter that is at least twice the initial diameter. The twice initial diameter of the inflatable balloon is relatively small to provide a reliable ablation surface. A common disadvantage of the prior art is the use of inflatable balloons that operate under internal pressure and a commensurate risk of sudden destruction and resultant injuring of the biological tissue to be treated.